The FBI has started a probe of a rogue Wall Street trader for alleged stock manipulation, The Post has learned.

The trader, identified by people familiar with the probe as David Miller, of Rochdale Securities, allegedly made an unauthorized purchase of 1.6 million shares of Apple — a $1 billion trade that has rocked the small brokerage and put it on the brink of extinction.

The errant trade, which was allegedly made Oct. 25, the day before the tech titan reported its fiscal fourth-quarter results, was first believed to be an honest mistake. However, it is now being looked at as part of a alleged market manipulation scheme to pocket millions in phony profits, sources said.

Regulators including the Securities and Exchange Commission and Finra have joined the FBI in the probe, sources said.

Miller has not returned to work since placing the trade.

“He walked out the door the next day and never came back,” said one person familiar with the situation.

A spokeswoman at FINRA declined to comment and calls to the FBI and the SEC were not immediately returned.

Miller is believed to be a 20-year broker-dealer veteran who had typically focused on the biotechnology sector.

Regulators and Rochdale are probing whether he was involved in similar transactions with other traders in an effort to make a profit for himself.

The Stamford, Conn.-based broker dealer is teetering on the brink of extinction and has talking to companies about making an equity infusion in the company.

The purchase was found and unwound the same day, sources say, explaining that he may have intentionally placed the trade as a part of a broader scheme with another trader outside the firm.